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Harvard epidemiologist dismantles CDC immunity study

Government offers fatally flawed research to counter Israeli data

By Art Moore Published November 2, 2021

Amid more than 100 studies showing the superiority of natural COVID-19 immunity over vaccine-produced immunity, the Centers for Disease Control released the results this week of a study claiming to show the opposite.

But Dr. Martin Kulldorf, who has worked on vaccine epidemiology since joining the Harvard faculty nearly two decades ago, is among many epidemiologists who have quickly pointed out the CDC study's fatal flaws.

Dr. Martin Kulldorf of Harvard University School of Medicine (Wikimedia Commons) In an article for the Brownstone Institute, he compared the CDC research with an Israeli study that found people vaccinated for COVID-19 are 27 times more likely to have a symptomatic COVID infection than those previously infected by the virus.

The Israeli study further found that the vaccinated were nine times more likely to be hospitalized for COVID than those with natural immunity.

The CDC study claims that the COVID recovered are five times more likely to be hospitalized for COVID than the vaccinated.

Kulldorf, noting both studies cannot be right, said he has never "never before seen such a large discrepancy between studies that are supposed to answer the same question."

Kulldorff is an epidemiologist, biostatistician and professor of Medicine at Harvard Medical School. He is the co-author, along with Dr. Jay Bhattacharya of Stanford and Dr. Sunetra Gupta of Oxford, of the Great Barrington Declaration, advocating a public policy of "focused protection" on the vulnerable while letting others go about their business. More than 860,000 people have signed the declaration, including 14,981 medical and public health scientists, and 44,167 medical practitioners.

As the federal and local governments double down on vaccine mandates, a new study by the Yale School of Public Health offers the latest evidence that the immunity acquired by COVID-19 infection is superior to the immunity from vaccination.

A total of 102 studies with the same conclusion has been compiled by Dr. Paul Elias Alexander and several other prominent colleagues.

The Israeli researchers said their analysis "demonstrated that natural immunity affords longer lasting and stronger protection against infection, symptomatic disease and hospitalization due to the delta variant."

Tracking patients over time

Among the elements that made the Israeli study more reliable, Kulldorf said, was the fact that, unlike the CDC study, it tracked a cohort of patients over time.

The Israeli researchers tracked 673,676 vaccinated people who they knew not to have had COVID and 62,833 unvaccinated COVID-recovered individuals. To make a fair and unbiased comparison, the researchers matched patients from the two groups on age, gender, geographical location and time since vaccination or the disease.

For the primary analysis, the study authors identified a cohort with 16,215 individuals who had recovered from COVID and 16,215 matched individuals who were vaccinated.

Ultimately, 191 patients in the vaccinated group and only eight in the COVID-recovered group got symptomatic COVID disease. After adjusting the statistical analysis for comorbidities, the researchers measured a relative risk of 27, meaning the vaccinated people were estimated to be 27 times more likely to be infected with COVID. (The authors, with 95% confidence, found the vaccinated were between 13 and 57 times more likely to be infected).

In the CDC study, instead of creating a cohort of people to follow over time, the researchers identified people hospitalized with COVID-like symptoms and then evaluated how many of them tested positive versus negative for COVID.

Among the vaccinated, 5% tested positive, while 9% were positive among the COVID-recovered.

Dr. Marty Makary of Johns Hopkins University was among the many other critics of the CDC study.

He said on Twitter that "journalists should not simply parrot this flawed" government study on natural immunity and should ask criticial questions, noting the authors admitted that "sparse data limited the precision" of their findings.

Kulldorf, who serves on scientific advisory committees to the FDA and the CDC, said that what the CDC authors do not mention is that they adopted "a de facto case-control design."

While it is a well-established epidemiological design, it is not as strong as a cohort study, the Harvard professor said.

Further, he argued, the controls did not constitute a representative sample from the population from which the COVID patients came.

That's because COVID-negative people with COVID-like symptoms, such as pneumonia, tend to be older and frailer with comorbidities. They are also more likely to be vaccinated.

"The problem is that the CDC study answers neither the direct question of whether vaccination or Covid recovery is better at decreasing the risk of subsequent Covid disease, nor whether the vaccine rollout successfully reached the frail," he wrote.

"Instead, it asks which of these two has the greater effect size. It answers whether vaccination or Covid recovery is more related to Covid hospitalization or if it is more related to other respiratory type hospitalizations."

Kulldorf pointed out that epidemiologists typically rely on case-control studies when data are unavailable for a whole cohort. But for this particular study, there is no good reason for it, since cohort data are available from multiple CDC data partners.

"It is surprising that CDC chose this case-control design rather than the less biased cohort design selected by the Israeli authors," he said. "Such an analysis would answer the question of interest and may have given a different result more in line with the Israeli study."

Essential workers with superior immunity being fired

The solid evidence provided by the Israeli study, he said, means there is no reason to prevent people with natural immunity from activities that are permitted to the vaccinated.

"In fact, it is discriminatory," he said.

Kulldorf noted that many of the COVID-recovered were exposed to the virus as essential workers during the height of the pandemic before vaccines were available.

"They kept the rest of society afloat, processing food, delivering goods, unloading ships, picking up garbage, policing the streets, maintaining the electricity network, putting out fires, and caring for the old and sick, to name a few," he said.

"They are now being fired and excluded despite having stronger immunity than the vaccinated work-from-home administrators that are firing them."

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